Ball grid arrays are well known in the art and available commercially. Such an array comprises a plastic film with an array of recesses, each recess providing a receptacle for a solder ball. The arrays are available in strips and the individual segments of the strip (i.e. array) can be detached from the strip.
The task of populating the recesses reliably is a difficult one and a number of procedures to accomplish reliable solder ball placement have been devised. One such procedure developed by Motorola, employs a vacuum chuck with a number of holes corresponding to the recesses in a ball grid array. The holes are defined in a shift plate which moves to release the ball into the ball grid array, properly positioned, when the vacuum is removed. Another method employs a "dip strip" which captures the balls and then mates the ball grid array to the "dip strip" to transfer the balls.
The above noted copending application discloses an alternative method for populating a ball grid array. The method employs gravity for transferring solder balls from a tooling plate to an awaiting ball grid array, positioned closely beneath the plate. The tooling plate and the ball grid array are fastened to a rotatable gantry or wheel. The wheel is rotated to move the pair of components, tooling plate down, through a reservoir of solder balls. The wheel is rotated further so that the tooling plate is positioned above the ball grid array for gravity transfer of the solder balls.